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Environmental Factors Relevant to Eelgrass in the Neponset River Estuary
Christina Ciarfella
Map 1. Area of Neponset River estuary evaluated and used for calculations
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SalinitypH
Temperature
Wave Action
Light Intensity
Flow Rate
Substrate
Dissolved Oxygen
InhibitorsTurbidity
Nitrogen
Grazers
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SalinitypH
Temperature
Wave Action
Light Intensity
Flow Rate
Substrate
Dissolved Oxygen
InhibitorsTurbidity
Nitrogen
Grazers
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Methods
• Processed MWRA physical data• Calculated light intensity using MWRA secchi
depths• Estuary Loading Model (NLOAD)• Processed MWRA chlorophyll a data• Reviewed literature and class assessments
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Source: MWRA website
Map 1. Area of Neponset River estuary evaluated and used for calculations
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Seasonsal Temperature by Year
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110
5
10
15
20
25
Figure 1: Seasonsal Temperature by Year in Neponset River Estuary
Jan-MarApr-JunJul-SepOct-Dec
Year
Tem
pera
ture
oC
Error bars are +/- 1 σ
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Seasonsal Salinity by Year
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110
5
10
15
20
25
30
35
Figure 2: Seasonsal Salinity by Year in Neponset River Estuary
Jan-MarApr-JunJul-SepOct-Dec
Year
Salin
ity (P
SU)
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Seasonal pH by Year
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110
1
2
3
4
5
6
7
8
9
Figure 3: Seasonsal pH by Year in Neponset River Estuary
Jan-MarApr-JunJul-SepOct-Dec
Year
pH
Error bars are +/- 1 σ
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Seasonsal Dissolved Oxygen by Year
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110
2
4
6
8
10
12
14
Figure 4: Seasonsal Dissolved Oxygen by Year in Neponset River Estuary
Jan-MarApr-JunJul-SepOct-Dec
Year
Diss
olve
d O
xyge
n (m
g/L)
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Seasonsal Turbidity by Year
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110
5
10
15
20
25
30
35
Figure 5: Seasonsal Turbidity by Year in Neponset River Estuary
Jan-MarApr-JunJul-SepOct-Dec
Year
Turb
idity
(NTU
)
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Table 2: Estimated Light Intensity
Station
Secchi depth (m) Site depth (m) Light intensity at
site depth (E/day)
39 1.56 3.94 1.32
40 1.56 2.96 3.84
41 1.44 5.90 0.10
42 1.19 5.80 0.02
54 0.98 6.02 0.003
84 1.69 6.46 0.15
89 1.19 2.12 4.77
140 1.89 8.25 0.058
Beers-Lambert Equation
Id = I0e-kd
Id = light intensity at site depth
I0 = light intensity at the surface
k = attentuation coefficient (1.7/secchi depth)
d = site depth
Light Intensity
*Id must equal 6.4-12.9E/day for growth
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Estuarine Loading Modal
Input Estimation Method/Source
Land and freshwater derived TDN load (kg per year) 820786.52 Output from NLM Model (phase 1 assessment nload.mbl.edu)
Open water area (ha) 217 Considered to be the same as surface area at high tide; data from Gardner, Chen & Berry 2005, via Lynn's AP1
Average depth (m) 4.21 Averaged all bottom depths within and between sites from MWRA physical data 1994-2011 (mwra.state.ma.us )
Tidal range (m) 3 Zhu & Olsen 2009 via Lynn's AP1
Tidal period (hrs per day) 6 Boston Tide Charts (boatma.com/tides)
Number of houses 259827 334.4 houses per square mile, converted to square km, multiplied by 300 km2 (census-charts.com)
Salt marsh area (ha) 107.513 Tiner et al. 1998; via Lynn's AP1
Eelgrass bed area (ha) 0 Eelgrass Mapping Project Viewer (mass.gov)
Total watershed area (ha) 33669.8 neponset.org/Watershed.htm
Length of estuary perimeter (m) 16000 Visual estimation using GIS (maps.google.com)
Flushing time of the freshwater reach (days) 0.063
Used the relative surface areas over tidal range (Gardner, Chen & Berry 2005, via Lynn's AP1) to calculate slope; assumed estuary was conic to calculate volume; used volume over flow rate to calculate flushing time.
Output: Net DIN loading in estuary is 666413.3kg N/year
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1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110
2
4
6
8
10
12
14
Figure 6: Seasonsal Chl a by Year in Neponset River Estuary
Jan-MarApr-JunJul-SepOct-Dec
Year
Chlo
roph
yll a
(µg/
L)
Error bars are +/- 1 σ
Inhibitors: phytoplankton & macroalgae
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http://birdway.com.au/anatidae/black_swan/source/black_swan_85609.htm
Potential Grazers
• Mute swan• Brant goose• Mallard• Wigeon• Pintail• Coot• Blue crab• Marsh crab • Amphipods• Isopods• Chink snail• Sea slugs
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Table 1: Summary of Factors, Methods & Results
Factor Source/Method Result
Temperature (oC) Processed MWRA Data
Min-Max (Mean) *Upstream: 0.58 - 25.39 (12.63)
Middle: 8.44 - 22.25 (16.24) Mouth: 3.53-20.89 (13.81)
Salinity (PSU) Processed MWRA Data
Min-Max (Mean) Upstream: 0.24 - 31.15 (25.55) Middle: 0.24 - 32.97 (26.91)
Mouth: 0.19 - 31.18 (24.24)
Dissolved Oxygen (mg/L) Processed MWRA Data
Min-Max (Mean) Upstream: 5.75 - 9.95 (7.45) Middle: 6.35 - 9.04 (7.76)
Mouth: 7.58 - 10.42 (8.73)
pH Processed MWRA Data
Min-Max (Mean) Upstream: 7.21 - 7.95 (7.74)
Middle: 7.29 - 7.96 (7.77) Mouth: 7.13 - 8.00 (7.76)
Turbidity (NTU) Processed MWRA Data
Min-Max (Mean) Upstream: 2.00 - 29.50 (11.51)
Middle: 2.40 - 29.85 (9.06) Mouth: 2.15 - 28.60(7.96)
Nitrogen ELM Model Net DIN: 666413.3 kg N per yr
Substrate Personal observation in class survey of the estuary Primarily mud
Flow Rate Lynn's AP1 (Breault 2002) 0.6 to 3.1 m3/s
Wave Action Literature (Rana 2007; seagrassli.org) Wave action may be negligible for eelgrass growth in Neponset
Light IntensityCalculated using Secchi data and Beers-Lambert equation (Id = I0e-kd)
Light Intensity at bottom may be insufficient to support eelgrass growth
Grazers Review of published and grey Literature Mute swans, Brant geese, chink snails, marsh and blue crabs are potential grazers in the Neponset
Inhibitors Processed MWRA Data (Chl a) Min-Max (Mean) (µg/L) ** Mouth: 0.22 - 12.4 (3.166)
*Upstream: site 055; Middle: sites 054, 042; Mouth: sites 039, 040, 041, 084, 089, 140 **Mouth: site 140